The present invention relates to an ink jet recording head in which piezoelectric transducers provided in parts of pressure chambers communicated with nozzle openings compress the pressure chambers to form ink droplets, and more particularly to an ink jet type recording head which is formed by arranging a nozzle plate, pressure chamber forming members and a vibrating plate one on another, and to a method for manufacturing the ink jet type recording head.
An ink jet type recording head is known in which piezoelectric transducers are coupled to diaphragms which form walls of respective ink pressure chambers, wherein displacement of the piezoelectric transducers varies the volume of the pressure chambers to thereby eject ink droplets. Such a recording head is advantageous in that, since the displacement of the diaphragms by the piezoelectric transducers takes place over a relatively large area of the pressure chambers, ink droplets can be formed stably.
However, the recording head is still disadvantageous in that, since ink droplets are jetted in a direction perpendicular to the direction of displacement of the diaphragm, the recording head is unavoidably large in the direction perpendicular to the surface of the recording sheet, and accordingly the carriage supporting and transporting the recording head and its related components are also unavoidably large in this direction.
In order to overcome the above-described difficulty, an ink jet type recording head has been proposed, for example, in Japanese Unexamined Patent Publication No. Sho. 62-111758, in which pressure generating members including diaphragms and ink flow path forming members are formed in a layered construction, and nozzle openings are provided in a row extending parallel to the direction of displacement of the diaphragm, thereby to reduce the thickness of the recording head. That is, the recording head has a layered structure.
The layered structure is advantageous in that the recording head can be miniaturized, and it can be manufactured using a simple method for joining plate members formed by pressing or etching.
In the manufacturing method for producing the recording head, an adhesive agent is used for joining the plate members. However, during manufacture, the adhesive agent can sometimes flow into small holes which form ink flow paths in the plate members, thus changing the ink flow resistance thereof, lowering the reliability in operation of the recording head. Furthermore, because the piezoelectric transducers must be fixed to the diaphragm with an adhesive agent or by etching or laser welding, the manufacture of the recording head requires much time and labor.
In order to eliminate the above-described difficulties, an ink jet type recording head has been proposed, for example, in Japanese Unexamined Patent Publication No. Sho. 63-149159, which is formed by layering ceramic plates in a semi-solid state, shaped as required to form flow path members, and piezoelectric transducers, one on another and subjecting the structure to firing. That is, the recording head is manufactured without a separate step of mounting the piezoelectric transducers. However, the method is still disadvantageous in that it cannot achieve a reduction in the thickness of the recording head since the nozzle openings extend in a direction perpendicular to the direction of displacement of the diaphragm, similar to the above-described recording head.
In view of the foregoing, an object of the invention is to provide an ink jet type recording head in which the manufacturing assembly accuracy is improved, the number of steps required for joining the relevant members is minimized, and the nozzle openings are provided in parallel with the direction of displacement of the diaphragms to reduce the thickness of the recording head.
Another object of the invention is provide a method for manufacturing such an ink jet type recording head.
In order to achieve the aforementioned objects of the invention, a multi-layer ink jet type recording head is manufactured according to the invention as follows: A first plate member of ceramic forming a vibrating member with piezoelectric transducers on the surface thereof, a first spacer member made of ceramic with a plurality of through-holes therein forming pressure chambers, and a lid member having through-holes through which the pressure chambers are communicated with a reservoir and are joined together to form a pressure generating unit in such a manner that the first plate member is placed on one surface of the first spacer member, and the lid member is sealingly set on the other surface of the spacer member. An ink supplying member made of a metal plate and which is connected through a flow path to an ink tank and has through-holes through which the pressure chambers are communicated with nozzle openings and the reservoir is communicated with the pressure chambers, a second spacer member having through-holes through which the pressure chambers are communicated with the reservoir and the nozzle openings, and a nozzle plate member with the nozzle openings formed therein are joined together to form a flow path unit in such a manner that the ink supplying member is placed on one surface of the second spacer member, and the nozzle plate member is fixedly placed on the other surface of the second spacer member. The outer surface of the lid member in the pressure generating unit is joined to the outer surface of the ink supplying member in the flow path unit with a macromolecular adhesive agent.
In the pressure generating unit, which is made of ceramic, small through-holes are formed in the spacer member, which simplifies the manufacturing step of joining the vibrating member, the spacer member and the lid member, and positively prevents leakage of ink past the unit, to which high pressure is exerted. The flow path unit, which is made of metal, has a relatively large through-hole to form the reservoir in the space member, and therefore it is high in dimensional accuracy. The pressure generating unit and the flow path unit are joined together with a macromolecular adhesive layer, so that the difference in thermal expansion between the two units, which are made of different materials as described above, can be absorbed.